Characterization and reduction of X‐gradient induced eddy currents in a NdFeB magnetic resonance imaging magnet‐3D finite element method‐based numerical studies
Characterization and reduction of X‐gradient induced eddy currents in a NdFeB magnetic resonance imaging magnet‐3D finite element method‐based numerical studies
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NdFeB 磁共振成像磁体中 X 梯度感应涡流的表征和减少 - 基于 3D 有限元方法的数值研究
DOI：
10.1002/cmr.b.20189
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
D. Xie
中科院分区：
文献类型：
--
作者：
Xia Li;L. Xia;Feng Liu;S. Crozier;D. Xie
在永磁磁共振成像（MRI）系统中，脉冲梯度场在磁体的导电结构中感应强涡电流。用于图像编码的梯度场被这些涡电流扰动，从而导致MR图像失真。减少涡流效应的传统方法是采用被动屏蔽（涡流板）。然而，被动屏蔽结构的分析通常是非最佳的。在本文中，一个全面的三维有限元法（FEM）模型的表征的铁磁材料的磁铁，这是有助于评估的屏蔽效果和被动屏蔽设计的改进。在数值分析过程中，通过X-梯度线圈引入涡流源，考虑了叠层硅钢结构的非线性和各向异性，并对有限元控制方程中惩罚因子的选取进行了详细说明。根据模拟结果，提出了被动屏蔽设计的建议。
In permanent magnetic resonance imaging (MRI) systems, pulsed gradient fields induce strong eddy currents in the conducting structures of the magnet. The gradient field for image encoding is perturbed by these eddy currents, thus leading to MR image distortions. The conventional approach for the reduction of the eddy current effects is to employ passive shielding (an eddy current board). However, the analysis of the passive shielding structure is typically nonoptimal. In this article, a comprehensive 3D finite element method (FEM) model for the characterization of eddy currents in the ferromagnetic materials of the magnet is developed, which is helpful for the evaluation of the shielding effects and the improvement of passive shielding designs. During the numerical analyses, the eddy current source was introduced through X-gradient coils, nonlinearity, and the anisotropy of the laminated silicon steel structure was considered, with the selection of a penalty factor in the FEM governing equations being also detailed. Based on the simulations results, suggestions have been made for passive shielding designs.
DOI：
10.1002/cmr.b.20115
发表时间：
2008-08
影响因子：
0.9
作者：
H. Kato;K. Kishi;N. Takahashi;J. Asaumi;Y. Honda;Y. Yanagi;M. Aoki
通讯作者：
H. Kato;K. Kishi;N. Takahashi;J. Asaumi;Y. Honda;Y. Yanagi;M. Aoki